The present invention involves a lift gate assembly utilized for loading and unloading of materials to be shipped, and in particular to a lift gate assembly that vertically supports a platform of the lift gate assembly from the associated vehicle while simultaneously preventing opening of the platform and retaining support members from free motion during operation of the vehicle.
Hydraulic lift gates are used in a wide variety of applications associated with trucks and trailers to facilitate the loading and unloading of cargo when the cargo is required to be vertically lifted from a loading surface, such as the ground or a dock surface, to the height of the vehicle cargo compartment floor, or lowered to the ground or dock surface from the height of the vehicle cargo compartment floor. Previous lift gate designs have performed this function by vertically extending and retracting telescoping columns to which a cargo platform is attached. When used for the loading or unloading of cargo in this manner, the platform is unfolded to a horizontal position, thereby protruding behind the rear of the associated vehicle to provide a surface onto which the cargo can be placed. When in storage, the platform is folded into a vertical position, thereby reducing the distance the platform extends from the rear of the associated vehicle. Several lift gates as known permit the platform to be positioned so as to allow ingress and egress of materials through a door opening of the vehicle, thereby allowing loading and unloading of the vehicle when the platform is in a storage position.
Other known lift gates include platforms that are comprised of at least two sections that are folded one against the other and stored in a vertical position adjacent the rear of the associated vehicle when the vehicle is in transit, or when being docked, and that are in a horizontal position forming one continuous section when the platform is folded and being used to raise or lower cargo.
Heretofore, the platform, whether formed of a single or multiple sections, is rotatably moved between the storage and load/unload positions by a motor operably coupled thereto. The associated motor prevents the platform from being rotated from a storage position to the load/unload position by applying a rotational force thereto. Moreover, it is common practice to provide the lift gate with one or more latch mechanisms to prevent the lift gate from unfolding and/or lowering inadvertently from the storage position. Previous designs of latches required the operator to manually operate the mechanism as attached to the columns or the platform, thereby requiring the operator to position themselves very close to the lift gate chancing injury. Other known designs include utilizing a plurality of mating wedges, wherein a wedge associated with the telescoping columns is coupled with a wedge associated with the platform. In this particular design, a constant upward force is required to be exerted by the telescoping columns, thereby keeping the wedges engaged and preventing the platform from falling from the storage position to the load/unload position.
Other known lift gates utilize chains or other flexible elements having one end connected to one of the column assemblies and another end connected to the platform, such that the chain supports the platform from the column assemblies when in the load/unload position. While the chains provide adequate support for the platform from the column assemblies, these chains are allowed to move freely with respect to the other components of the lift gate and the associated vehicle when the platform is in the storage position, thereby allowing the chains to possibly damage components of the lift gate and the associated vehicle, as well as the aesthetic appearance of the vehicle.
A lift gate assembly is needed that provides adequate retention and support of an associated platform in a raised storage position, allows for storage of the platform at various heights with respect to an associated vehicle door, and that prevents support elements used to support the platform in a lowered in-use position from damaging other components of the lift gate assembly or the aesthetic appearance of the associated vehicle when in a raised storage position.